1. Field of the Invention
The present invention relates to an analytical electron microscope. It also relates to a method of operating such an electron microscope.
2. Summary of the Prior Art
In an analytical electron microscope, an electron beam is generated and caused to be incident on a sample to be investigated. The beam is controlled and focused by suitable electron lenses. There are several types of analyzers that may then be used in conjunction with the analytical electron microscope to determine the effect of the sample on the electron beam. Since an analytic electron microscope operates by transmission, it is possible to determine the energy loss of electrons of the beam which interact with the sample, using a detecting device known as an electron energy loss spectrometer (EELS). Also known is a detecting device known as an energy dispersive X-ray analyzer (EDX) which detects the element or elements present in the sample to be determined. The electron microscope can be operated to various configuration, so that it acts as a convergent electron beam diffraction device, (CBED). This permits the shape (i.e. surface configuration) of the sample to be detected.
Proposals have been made to automate control of the incidence of the electron beam on the sample. For example, automatic control of axial alignment, astigmatic adjustment and focusing have been automated. Examples of such automation are disclosed in JP-B-A-56-7338, JP-A-58-19423, JP-A-3-152846, JP-A-3-194839 and U.S. Pat. No. 4,871,912.
However, the subsequent analysis in known systems depends on the skill of the operator. The output of the various detecting devices that may be used, e.g. EDX, EELS or CBED, are displayed on a suitable display. When an object, such as a dislocation or grain boundary is present within the object, the operator can detect the presence and the type of such an object on the basis of experience, since each object will produce a different effect in one or more of the detectors. However, a high level of skill is required if the operator is successfully to distinguish the many types of objects that may be present in the sample.